1. Field of the Invention
The present invention relates to an article transport facility comprising a travel rail and an article transport vehicle that includes a power receiving portion to which driving electric power is supplied contactlessly from an electricity supply line provided along the travel rail and that is capable of traveling while being guided by the travel rail.
2. Description of the Related Art
Article transport facilities such as one described above are article transport facilities in which articles are transported along the tracks, and in which electric power to allow article transport vehicles is supplied from an electricity supply line arranged along travel rails to a power receiving portion provided to the article transport vehicles without contact. And in order to properly supply electricity to the power receiving portion from the electricity supply line, the positional relationship between the electricity supply line and the power receiving portion must be maintained within a proper range in which electric power can be supplied (for example, range in which the power receiving portion and the electricity supply line overlap each other in the vertical direction). To this end, by arranging the electricity supply line to extend along the travel rail, and by having the article transport vehicles travel along the travel rail, article transport vehicles are caused to travel while maintaining the positional relationship, in the lateral direction of the article transport vehicle, between the electricity supply line and the power receiving portion to be within a proper range in which electric power can be supplied.
In such article transport facility of a type where articles are transported along the tracks, predetermined travel paths are formed by combining straight portions and curved portions as travel paths along which the article transport vehicle travel. And the travel rails and the electricity supply lines are arranged to extend along the set travel paths. And in order to allow the article transport vehicles to travel smoothly even in curved portions of the predetermined travel paths, the article transport vehicles include guide wheels which are guided with respect to the horizontal direction by contacting the travel rail, and a travel portion having travel wheels which contact and are drivingly rotated on, the travel rail, with the travel portion rotatably connected about a vertical axis to a vehicle main body portion with a connecting shaft. Thus, when an article transport vehicle travels in a curved portion of a predetermined travel path, the travel portion rotates about the vertical axis with respect to the vehicle main body portion by means of the connecting shaft as the travel portion travels along the travel rail. This allows article transport vehicles to travel smoothly even in curved portions.
As described above, the travel portion travels along the travel rail as it rotates about the vertical axis with respect to the vehicle main body portion. Therefore, when a pair of front and back travel portions is provided, for example, the trajectory of the vehicle main body portion is displaced from a trajectory that extends along the curved portion (i.e., the trajectory is displaced inwardly from one that extends along the curved portion) whereas the trajectory of the travel portion extends along the curved portion. Especially, for example, when the curved portion is formed to have a circular shape, the smaller the radius of the curved portion is, to the greater degree the trajectory of the vehicle main body is displaced from a trajectory that extends along the curved portion. Thus, when the power receiving portion is provided to the vehicle main body, the power receiving portion will move inwardly of the curved portion in the curved portion with respect to the electricity supply line arranged along the curved portion, which increases the distance between the electricity supply line and the power receiving portion in the lateral direction of the article transport vehicle. It thus becomes impossible to maintain the positional relationship, between the electricity supply line and the power receiving portion in the lateral direction of the article transport vehicle, to be within a proper range in which electric power can be supplied. And it may become impossible to properly supply electricity from the electricity supply line to the power receiving portion.
To this end, in a conventional article transport facility, the power receiving portion is configured to be rotatable about a vertical axis with respect to the vehicle main body by means of an vertically extending axis. And the power receiving portion is provided with a roller which contacts the travel rail to be guided thereby and a spring that urges the roller into contact with the travel rail (see, for example, Patent Document 1). In the facility of Patent Document 1, the roller contacts the travel rail to be guided thereby under the urging force of the spring when traveling in a curved portion, and the power receiving portion rotates about the vertical axis with respect to the vehicle main body and thus moves along the travel rail. Therefore, since the trajectory of the power receiving portion in a curved portion becomes a trajectory that extends along the curved portion, the positional relationship between the electricity supply line and the power receiving portion can be maintained within a proper range in which electric power can be supplied, making it possible for electricity to be properly supplied to the power receiving portion from the electricity supply line.